Thermal management of steering system for autonomous vehicles

ABSTRACT

Aspects of the disclosure relate to a vehicle having an autonomous driving mode and a manual driving mode. The vehicle may include a steering system having one or more processors configured to control the orientation of the one or more wheels based on control commands. The vehicle may also include an autonomous driving control system configured to control the vehicle in an autonomous driving mode by generating the control commands and to send the control commands to the steering system. In addition, the steering system may thermally derate the steering system based on first temperature information for the steering system when the vehicle is operating in a manual drive mode, and the autonomous driving control system may thermally derate the steering system based on second temperature information for the steering system when the vehicle is operating in the autonomous driving mode.

BACKGROUND

Some vehicles may operate in various modes which provide differentlevels of control to a driver. For instance, typical vehicles mayoperate in manual driving modes, where a human operator or drivercontrols acceleration, deceleration, and steering of the vehicle as wellas semi-autonomous driving mode, such as cruise control, where acomputer of the vehicle controls acceleration and deceleration while adriver controls steering, etc. In some instances, these vehicles mayalso operate in autonomous driving modes where the computer of thevehicle controls all of braking, all of the acceleration, decelerationand steering of the vehicle without continuous input from a driver orpassenger. In the autonomous driving mode, the passenger may providesome initial input, such as a destination location, and the vehiclemaneuvers itself to that destination.

Typical electronic power steering systems may self-manage thetemperature of internal components and thermally derate or limit systemoutput to stay below certain temperature thresholds. This may beachieved by the steering system comparing a measured or estimatedtemperature of the steering system (or a component of the steeringsystem) to one or more temperature thresholds and generating a flagand/or signals to derate the steering system for instance, by limitingtorque and/or steering rate, or even shutting down completely andleaving only unassisted manual control for the driver. The derating mayalso involve preventing the motor of the steering system from producingcertain torque values. Human drivers may respond by further rotating asteering wheel to provide additional torque.

BRIEF SUMMARY

Aspects of the disclosure provide a vehicle. The vehicle includes asteering system having one or more processors configured to control theorientation of one or more wheels of the vehicle based on controlcommands as well as an autonomous driving control system having one orprocessors. The one or more processors are configured to control thevehicle in an autonomous driving mode by generating the controlcommands, and send the control commands to the steering system. Inaddition, the one or more processors of the steering system areconfigured to thermally derate the steering system based on firsttemperature information for the steering system when the vehicle isoperating in a manual drive mode. The one or more processors of theautonomous driving control system are further configured to thermallyderate the steering system based on second temperature information forthe steering system when the vehicle is operating in the autonomousdriving mode.

In one example, the one or more processors of the autonomous drivingcontrol system are further configured to, when operating in theautonomous driving mode, limit thermal derating in order to enable atype of maneuver that the vehicle needs to perform to avoid an object.In this example, the type of maneuver includes a steering maneuver toavoid an object. Alternatively, the type of maneuver includes pullingthe vehicle over in response to a fault with the autonomous drivingcontrol system. In another example, the one or more processors of theautonomous driving control system are further configured to, when thevehicle is operating in the autonomous driving mode, limit thermalderating when the vehicle is traveling at speed greater than apredetermined threshold speed. In another example, when the vehicle isoperating in the autonomous driving mode, the one or more processors ofthe steering system are further configured to ignore temperatureinformation generated by the steering system. In another example, whenthe vehicle is operating in the autonomous driving mode, the one or moreprocessors of the steering system are further configured to ignore anythermal derating signals generated at the steering system. In anotherexample, the one or more processors of the steering system are furtherconfigured to distinguish between the control commands and signalsgenerated by manual operation of a steering input of the vehicle. Inanother example, the one or more processors of the steering system arefurther configured to distinguish between the control commands andsignals generated by manual operation of a steering input of the vehiclebased on content of the control commands and the signals. In anotherexample, the one or more processors of the steering system are furtherconfigured to distinguish between the control commands and signalsgenerated by manual operation of a steering input of the vehicle usingdifferent interfaces for receiving the control commands and the signals.In another example, the one or more processors of the steering systemare further configured to cause the vehicle to switch from theautonomous driving mode to the manual driving mode when thermal deratingreduces available torque at the one or more wheels below a predeterminedamount.

Another aspect of the disclosure provides a method of operating avehicle having a manual driving mode and an autonomous driving mode. Themethod includes controlling, by one or more processors of an autonomousdriving control system, the vehicle in the autonomous driving mode bygenerating control commands and sending the control commands to asteering system having one or more processors; using the steering systemto control the orientation of the one or more wheels based on controlcommands; using, by the one or more processors of the steering system,first temperature information for the steering system to thermallyderate the steering system when the vehicle is operating in the manualdrive mode; and using, by the one or more processors of the autonomousdriving control system, second temperature information for the steeringsystem to thermally derate the steering system when the vehicle isoperating in the autonomous driving mode.

In one example, the method also includes the vehicle is operating theautonomous mode, overriding any thermal derating in order to enable atype of maneuver that the vehicle needs to perform to avoid an object.In this example, the type of maneuver includes a steering maneuver toavoid an object. Alternatively, the type of maneuver includes pullingthe vehicle over in response to a fault with the autonomous drivingcontrol system. In another example, the method also includes, when thevehicle is operating in the autonomous driving mode, overriding anythermal derating when the vehicle is traveling at speed greater than apredetermined threshold speed. In another example, the method alsoincludes, when the vehicle is operating in the autonomous driving mode,ignoring, by the one or more processors of the steering system,temperature information generated by the steering system. In anotherexample, the method also includes, when the vehicle is operating in theautonomous driving mode, ignoring, by the one or more processors of thesteering system, any thermal derating signals generated at the steeringsystem. In another example, the method also includes, causing, by theone or more processors of the steering system, the vehicle to switchfrom the autonomous driving mode to the manual driving mode when thermalderating reduces available torque at the one or more wheels below apredetermined amount.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of an example vehicle in accordance withan exemplary embodiment.

FIGS. 2A and 2B are example functional diagrams of a steering system inaccordance with aspects of the disclosure.

FIG. 3 is an example external view of a vehicle in accordance withaspects of the disclosure.

FIG. 4 is a pictorial diagram of an example system in accordance withaspects of the disclosure.

FIG. 5 is a functional diagram of the system of FIG. 4 in accordancewith aspects of the disclosure.

FIG. 6 is an example flow diagram in accordance with aspects of thedisclosure.

DETAILED DESCRIPTION Overview

The technology relates to thermal management of steering systems forautonomous vehicles. As noted above, typical electronic power steeringsystems may self-manage the temperature of internal components andthermally derate or limit system output to stay below certaintemperature thresholds. This may be achieved by the steering systemcomparing a measured or estimated temperature of the steering system (ora component of the steering system) to one or more temperaturethresholds and generating a flag and/or signals to derate the steeringsystem, for instance bye. limiting torque and/or steering rate, or evenshutting down completely and leaving only unassisted manual control forthe driver. The derating may also involve preventing the motor of thesteering system from producing certain torque values. Human drivers mayrespond by further rotating a steering wheel to provide additionaltorque.

For vehicles which can operate fully autonomously, that is without adriver, there may be no human backup. At the same time, in certainsituations, limiting torque without considering the situational contextand the criticality of maneuvers to be executed, can create dangeroussituations. To avoid this, the autonomous driving control system may beenabled to command maneuvers which will increase the thermal load on thesteering system even after such temperature thresholds were reached whendeemed necessary.

To do so, the vehicle may be configured to allow different systems toimplement thermal derating depending on whether the vehicle is operatingin a manual driving mode, such as the first driving mode, or in anautonomous driving mode, such as the second or third driving mode. Forinstance, the steering system may control its own thermal derating whenthe vehicle is operating in the manual mode, and the autonomous drivingcontrol system may implement the thermal derating when operating in theautonomous driving modes.

When the vehicle is being operated in the manual driving mode or anyautonomous driving mode, the steering system may generate temperatureinformation identifying a measured or estimated temperature of thesteering system or one or more specific components of the steeringsystem. In this regard, the steering system include one or moretemperature sensors such as thermistors, thermometers, etc. or otherdevices for measuring different parameters in order to measuretemperature. The steering system and/or the autonomous driving controlsystem may use feedback from these temperatures sensors or other sourcesto determine temperature information for the steering system.

For instance, when the vehicle is operating in the manual driving mode,the steering system may compare the temperature information to one ormore threshold. When the measured or estimated temperature of one ormore components of the steering system meets or is greater than one ormore maximum thresholds, the steering system may automatically limit theamount of torque applied in order to reduce the likelihood of furtherincreasing the temperature of the components and causing long-termdamage to the hardware.

When the vehicle is operating in an autonomous driving mode, theautonomous driving control system may also determine when to implementthe derating. Like the steering system, the autonomous driving controlsystem may also receive and/or determine the temperature information andcompare this information to the one or more maximum temperaturethresholds. Based on whether any of these maximum temperature thresholdsare met, the autonomous driving control system may limit the steeringangle and/or torque at the wheels or by reducing a maximum torqueavailable to control the orientation of the one or more wheels, andthereby automatically attempting to reduce the temperature of thesteering system or one or more specific components of the steeringsystem.

Because the thermal derating is implemented at the autonomous drivingcontrol system when the vehicle is operating in an autonomous drivingmode, in the event of a safety critical situation, the autonomousdriving control system may be able to limit or prevent the thermalderating. Safety critical situations may include situations which wouldotherwise result in the vehicle colliding with another object or wouldprevent the vehicle from pulling over in an emergency.

The features described herein may provide for a useful and practicalapproach to addressing thermal derating for autonomous vehicles in a waywhich may improve overall safety of these vehicles. By moving thethermal derating functionality of the steering system into theautonomous driving control system when in an autonomous driving mode,this enables the vehicle to respond to safety critical situationsregardless of whether the steering system would otherwise have beenderating itself.

Example Systems

As shown in FIG. 1, a vehicle 100 in accordance with one aspect of thedisclosure includes various components. While certain aspects of thedisclosure are particularly useful in connection with specific types ofvehicles, the vehicle may be any type of vehicle including, but notlimited to, cars, trucks, motorcycles, buses, recreational vehicles,etc. The vehicle may have one or more computing devices, such ascomputing device 110 containing one or more processors 120, memory 130and other components typically present in general purpose computingdevices.

The memory 130 stores information accessible by the one or moreprocessors 120, including instructions 134 and data 132 that may beexecuted or otherwise used by the processor 120. The memory 130 may beof any type capable of storing information accessible by the processor,including a non-transitory computing device-readable or othermachine-readable medium, or other medium that stores data that may beread with the aid of an electronic device, such as a hard-drive, memorycard, ROM, RAM, DVD or other optical disks, as well as otherwrite-capable and read-only memories. Systems and methods may includedifferent combinations of the foregoing, whereby different portions ofthe instructions and data are stored on different types of media.

The instructions 134 may be any set of instructions to be executeddirectly (such as machine code) or indirectly (such as scripts) by theprocessor. For example, the instructions may be stored as computingdevice code on the computing device-readable medium. In that regard, theterms “instructions” and “programs” may be used interchangeably herein.The instructions may be stored in object code format for directprocessing by the processor, or in any other computing device languageincluding scripts or collections of independent source code modules thatare interpreted on demand or compiled in advance. Functions, methods androutines of the instructions are explained in more detail below.

The data 132 may be retrieved, stored or modified by processor 120 inaccordance with the instructions 134. For instance, although the claimedsubject matter is not limited by any particular data structure, the datamay be stored in computing device registers, in a relational database asa table having a plurality of different fields and records, XMLdocuments or flat files. The data may also be formatted in any computingdevice-readable format.

The one or more processor 120 may be any conventional processors, suchas commercially available CPUs or GPUs. Alternatively, the one or moreprocessors may be a dedicated device such as an ASIC or otherhardware-based processor. Although FIG. 1 functionally illustrates theprocessor, memory, and other elements of computing device 110 as beingwithin the same block, it will be understood by those of ordinary skillin the art that the processor, computing device, or memory may actuallyinclude multiple processors, computing devices, or memories that may ormay not be stored within the same physical housing. For example, memorymay be a hard drive or other storage media located in a housingdifferent from that of computing device 110. Accordingly, references toa processor or computing device will be understood to include referencesto a collection of processors or computing devices or memories that mayor may not operate in parallel.

Computing devices 110 may include all of the components normally used inconnection with a computing device such as the processor and memorydescribed above as well as a user input 150 (e.g., a mouse, keyboard,touch screen and/or microphone), various electronic displays (e.g., amonitor having a screen or any other electrical device that is operableto display information), and speakers 154 to provide information to apassenger of the vehicle 100 as needed. For example, electronic display152 may be located within a cabin of vehicle 100 and may be used bycomputing devices 110 to provide information to passengers within thevehicle 100.

Computing devices 110 may also include one or more wireless networkconnections 156 to facilitate communication with other computingdevices, such as the client computing devices and server computingdevices described in detail below. The wireless network connections mayinclude short range communication protocols such as Bluetooth, Bluetoothlow energy (LE), cellular connections, as well as various configurationsand protocols including the Internet, World Wide Web, intranets, virtualprivate networks, wide area networks, local networks, private networksusing communication protocols proprietary to one or more companies,Ethernet, WiFi and HTTP, and various combinations of the foregoing.

The computing devices 110 may be a part of an autonomous driving controlsystem for the vehicle and may be capable of communicating with variouscomponents of the vehicle in order to control the vehicle in anautonomous driving mode, such as the first and second autonomous drivingmodes discussed further below. For example, returning to FIG. 1, thecomputing devices 110 may be in communication with various systems ofvehicle 100, such as steering system 160, deceleration system 162,acceleration system 164, routing system 166, planning system 168,positioning system 170, and perception system 172 in order to controlthe movement, speed, etc. of vehicle 100 in accordance with theinstructions 134 of memory 130 in the autonomous driving mode.

As an example, the computing devices 110 may interact with decelerationsystem 162 and acceleration system 164 in order to control the speed ofthe vehicle. Similarly, steering system 160 may be used by computingdevices 110 in order to control the direction of vehicle 100. Forexample, if vehicle 100 is configured for use on a road, such as a caror truck, the steering system 160 may include components to control theangle of wheels to turn the vehicle as discussed further below. Thecomputing devices 110 may also use the signaling system in order tosignal the vehicle's intent to other drivers or vehicles, for example,by lighting turn signals or brake lights when needed.

Routing system 166 may be used by the computing devices 110 in order togenerate a route to a destination. Planning system 168 may be used bycomputing device 110 in order to follow the route. In this regard, theplanning system 168 and/or routing system 166 may store detailed mapinformation, e.g., highly detailed maps identifying a road networkincluding the shape and elevation of roadways, lane lines,intersections, crosswalks, speed limits, traffic signals, buildings,signs, real time traffic information, pullover spots, vegetation, orother such objects and information.

The routing system 166 may use the map information to determine a routefrom a current location (e.g. a location of a current node) to adestination. Routes may be generated using a cost-based analysis whichattempts to select a route to the destination with the lowest cost.Costs may be assessed in any number of ways such as time to thedestination, distance traveled (each edge may be associated with a costto traverse that edge), types of maneuvers required, convenience topassengers or the vehicle, etc. Each route may include a list of aplurality of nodes and edges which the vehicle can use to reach thedestination. Routes may be recomputed periodically as the vehicletravels to the destination.

Positioning system 170 may be used by computing devices 110 in order todetermine the vehicle's relative or absolute position on a map or on theearth. For example, the positioning system 170 may include a GPSreceiver to determine the device's latitude, longitude and/or altitudeposition. Other location systems such as laser-based localizationsystems, inertial-aided GPS, or camera-based localization may also beused to identify the location of the vehicle. The location of thevehicle may include an absolute geographical location, such as latitude,longitude, and altitude, a location of a node or edge of the roadgraphas well as relative location information, such as location relative toother cars immediately around it which can often be determined with lessnoise that absolute geographical location.

The positioning system 170 may also include other devices incommunication with the computing devices computing devices 110, such asan accelerometer, gyroscope or another direction/speed detection deviceto determine the direction and speed of the vehicle or changes thereto.By way of example only, an acceleration device may determine its pitch,yaw or roll (or changes thereto) relative to the direction of gravity ora plane perpendicular thereto. The device may also track increases ordecreases in speed and the direction of such changes. The device'sprovision of location and orientation data as set forth herein may beprovided automatically to the computing device 110, other computingdevices and combinations of the foregoing.

The perception system 172 also includes one or more components fordetecting objects external to the vehicle such as other vehicles,obstacles in the roadway, traffic signals, signs, trees, etc. Forexample, the perception system 172 may include lasers, sonar, radar,cameras and/or any other detection devices that record data which may beprocessed by the computing devices of the computing devices 110. In thecase where the vehicle is a passenger vehicle such as a minivan, theminivan may include a laser or other sensors mounted on the roof orother convenient location. For instance, FIG. 3 is an example externalview of vehicle 100. In this example, roof-top housing 310 and domehousing 312 may include a LIDAR sensor as well as various cameras andradar units. In addition, housing 320 located at the front end ofvehicle 100 and housings 330, 332 on the driver's and passenger's sidesof the vehicle may each store a LIDAR sensor. For example, housing 330is located in front of driver door 360. Vehicle 100 also includeshousings 340, 342 for radar units and/or cameras also located on theroof of vehicle 100. Additional radar units and cameras (not shown) maybe located at the front and rear ends of vehicle 100 and/or on otherpositions along the roof or roof-top housing 310.

The computing devices 110 may be capable of communicating with variouscomponents of the vehicle in order to control the movement of vehicle100 according to primary vehicle control code of memory of the computingdevices 110. For example, returning to FIG. 1, the computing devices 110may include various computing devices in communication with varioussystems of vehicle 100, such as deceleration system 162, accelerationsystem 164, steering system 160, routing system 166, planning system168, positioning system 170, perception system 172, and power system 178(i.e. the vehicle's engine or motor) in order to control the movement,speed, etc. of vehicle 100 in accordance with the instructions 134 ofmemory 130.

The various systems of the vehicle may function using autonomous vehiclecontrol software in order to determine how to and to control thevehicle. As an example, a perception system software module of theperception system 172 may use sensor data generated by one or moresensors of an autonomous vehicle, such as cameras, LIDAR sensors, radarunits, sonar units, etc., to detect and identify objects and theircharacteristics. These characteristics may include location, type,heading, orientation, speed, acceleration, change in acceleration, size,shape, etc. In some instances, characteristics may be input into abehavior prediction system software module which uses various behaviormodels based on object type to output a predicted future behavior for adetected object. In other instances, the characteristics may be put intoone or more detection system software modules, such as a traffic lightdetection system software module configured to detect the states ofknown traffic signals, construction zone detection system softwaremodule configured to detect construction zones from sensor datagenerated by the one or more sensors of the vehicle as well as anemergency vehicle detection system configured to detect emergencyvehicles from sensor data generated by sensors of the vehicle. Each ofthese detection system software modules may uses various models tooutput a likelihood of a construction zone or an object being anemergency vehicle. Detected objects, predicted future behaviors, variouslikelihoods from detection system software modules, the map informationidentifying the vehicle's environment, position information from thepositioning system 170 identifying the location and orientation of thevehicle, a destination location or node for the vehicle as well asfeedback from various other systems of the vehicle may be input into aplanning system software module of the planning system 168. The planningsystem 168 may use this input to generate trajectories for the vehicleto follow for some brief period of time into the future based on a routegenerated by a routing module of the routing system 166. In this regard,the trajectories may define the specific characteristics ofacceleration, deceleration, speed, etc. to allow the vehicle to followthe route towards reaching a destination. A control system softwaremodule of the computing devices 110 may be configured to controlmovement of the vehicle, for instance by controlling braking,acceleration and steering of the vehicle, in order to follow atrajectory.

The computing devices 110 may control the vehicle in an autonomousdriving mode by controlling various components. For instance, by way ofexample, the computing devices 110 may navigate the vehicle to adestination location completely autonomously using data from thedetailed map information and planning system 168. The computing devices110 may use the positioning system 170 to determine the vehicle'slocation and perception system 172 to detect and respond to objects whenneeded to reach the location safely. Again, in order to do so, computingdevice 110 and/or planning system 168 may generate trajectories andcause the vehicle to follow these trajectories, for instance, by causingthe vehicle to accelerate (e.g., by supplying fuel or other energy tothe engine or power system 174 by acceleration system 164), decelerate(e.g., by decreasing the fuel supplied to the engine or power system174, changing gears, and/or by applying brakes by deceleration system162), change direction (e.g., by turning the front or rear wheels ofvehicle 100 by steering system 160), and signal such changes (e.g., bylighting turn signals). Thus, the acceleration system 164 anddeceleration system 162 may be a part of a drivetrain that includesvarious components between an engine of the vehicle and the wheels ofthe vehicle. Again, by controlling these systems, computing devices 110may also control the drivetrain of the vehicle in order to maneuver thevehicle autonomously.

Computing device 110 of vehicle 100 may also receive or transferinformation to and from other computing devices, such as those computingdevices that are a part of the transportation service as well as othercomputing devices. FIGS. 4 and 5 are pictorial and functional diagrams,respectively, of an example system 400 that includes a plurality ofcomputing devices 410, 420, 430, 440 and a storage system 450 connectedvia a network 460. System 400 also includes vehicle 100A and vehicle100B, which may be configured the same as or similarly to vehicle 100.Although only a few vehicles and computing devices are depicted forsimplicity, a typical system may include significantly more.

As shown in FIG. 5, each of computing devices 410, 420, 430, 440 mayinclude one or more processors, memory, data and instructions. Suchprocessors, memories, data and instructions may be configured similarlyto one or more processors 120, memory 130, data 132, and instructions134 of computing device 110.

The network 460, and intervening graph nodes, may include variousconfigurations and protocols including short range communicationprotocols such as Bluetooth, Bluetooth LE, the Internet, World Wide Web,intranets, virtual private networks, wide area networks, local networks,private networks using communication protocols proprietary to one ormore companies, Ethernet, WiFi and HTTP, and various combinations of theforegoing. Such communication may be facilitated by any device capableof transmitting data to and from other computing devices, such as modemsand wireless interfaces.

In one example, one or more computing devices 410 may include one ormore server computing devices having a plurality of computing devices,e.g., a load balanced server farm, that exchange information withdifferent nodes of a network for the purpose of receiving, processingand transmitting the data to and from other computing devices. Forinstance, one or more computing devices 410 may include one or moreserver computing devices that are capable of communicating withcomputing device 110 of vehicle 100 or a similar computing device ofvehicle 100A or vehicle 100B as well as computing devices 420, 430, 440via the network 460. For example, vehicles 100, 100A, 100B, may be apart of a fleet of vehicles that can be dispatched by server computingdevices to various locations. In this regard, the server computingdevices 410 may function as a fleet management system (hereafter fleetmanagement system 410) which can be used to dispatch vehicles such asvehicles 100, 100A, 100B to different locations in order to pick up anddrop off passengers. In addition, the fleet management system 410 mayuse network 460 to transmit and present information to a user, such asuser 422, 432, 442 on a display, such as displays 424, 434, 444 ofcomputing devices 420, 430, 440. In this regard, computing devices 420,430, 440 may be considered client computing devices.

As shown in FIG. 5, each client computing device 420, 430, 440 may be apersonal computing device intended for use by a user 422, 432, 442, andhave all of the components normally used in connection with a personalcomputing device including a one or more processors (e.g., a centralprocessing unit (CPU)), memory (e.g., RAM and internal hard drives)storing data and instructions, a display such as displays 424, 434, 444(e.g., a monitor having a screen, a touch-screen, a projector, atelevision, or other device that is operable to display information),and user input devices 426, 436, 446 (e.g., a mouse, keyboard,touchscreen or microphone). The client computing devices may alsoinclude a camera for recording video streams, speakers, a networkinterface device, and all of the components used for connecting theseelements to one another.

Although the client computing devices 420, 430, and 440 may eachcomprise a full-sized personal computing device, they may alternativelycomprise mobile computing devices capable of wirelessly exchanging datawith a server over a network such as the Internet. By way of exampleonly, client computing device 420 may be a mobile phone or a device suchas a wireless-enabled PDA, a tablet PC, a wearable computing device orsystem, or a netbook that is capable of obtaining information via theInternet or other networks. In another example, client computing device430 may be a wearable computing system, shown as a wristwatch as shownin FIG. 4. As an example the user may input information using a smallkeyboard, a keypad, microphone, using visual signals with a camera, or atouch screen.

In some examples, client computing device 420 may be a mobile phone usedby passenger of a vehicle. In other words, user 422 may represent apassenger. In addition, client communication device 430 may represent asmart watch for a passenger of a vehicle. In other words, user 432 mayrepresent a passenger. The client communication device 440 may representa workstation for an operations person, for example, a remote assistanceoperator or someone who may provide remote assistance to a vehicleand/or a passenger. In other words, user 442 may represent a remoteassistance operator. Although only a few passengers and operationsperson are shown in FIGS. 4 and 5, any number of such, passengers andremote assistance operators (as well as their respective clientcomputing devices) may be included in a typical system.

As with memory 130, storage system 450 can be of any type ofcomputerized storage capable of storing information accessible by theserver computing devices 410, such as a hard-drive, memory card, ROM,RAM, DVD, CD-ROM, write-capable, and read-only memories. In addition,storage system 450 may include a distributed storage system where datais stored on a plurality of different storage devices which may bephysically located at the same or different geographic locations.Storage system 450 may be connected to the computing devices via thenetwork 460 as shown in FIGS. 4 and 5, and/or may be directly connectedto or incorporated into any of the computing devices 110, 410, 420, 430,440, etc.

Storage system 450 may store various types of information as describedin more detail below. This information may be retrieved or otherwiseaccessed by a server computing device, such as one or more servercomputing devices of the fleet management system 410, in order toperform some or all of the features described herein.

Returning to FIG. 1, the steering system 160 may be a typical rack andpinion steering system, torque overlay system, or a drive-by-wire systemwhich enables control of the steering by electrical signals rather thanby physical connections between the steering wheel and the vehicle'swheels. For example, a rack and pinion steering system may include anelectric motor and associated power electronics which may be used tolinearly displace a rack bar. The rack bar may be contained within ahousing that is attached to the vehicle chassis, and the rack bar itselfmay be attached to tie rod assemblies which translate the linear motionof the rack bar into rotational motion of the front suspension uprightassemblies. Also connected to the rack bar may be a pinion shaft withone or more intermediate shafts that connect to the steering column andsteering handwheel.

The torque overlay steering system, such as those used in commercialvehicles and trucks, may include an electric motor that rotates thepitman arm with the assistance of the hydraulics in the base gear. Thebase steering gear may be a combination of multiple advantages and isattached to the ladder frame of the truck. Also, the input shaft of thebase gear may be connected to at the steering hand wheel via thesteering column. A pitman arm connects the output of the base gear toone of the wheel ends at the steer axle. Further, both the wheel ends atthe steer axle may be connected by a tie-rod linkage. So any angularmotion in the pitman arm leads to angular motion of the wheels.

When operating in an autonomous driving mode, the autonomous drivingcontrol system may control the orientation of the vehicle's wheels bysending control commands as electrical signals from the computingdevices 110 to the steering system 160. These control commands mayinclude signals identifying steering control position as an angle and/orrack position (for rack and pinion style steering systems). The steeringcontrol position may define a desired position of the vehicle's wheelsrelative to the vehicle (e.g. 0 degrees being in the forward position)or position of the rack for following a trajectory generated by theplanning system 168. A non-linear transfer function may be used totranslate the linear displacement of the rack bar into an estimatedsteering control position. The steering system may use the steeringcontrol position to control the orientation of the vehicle (e.g. bycontrolling the operation of a motor of the steering system) inaccordance with a trajectory generated by a planning system of theautonomous driving control system without requiring input to a steeringwheel.

FIGS. 2A and 2B are a functional diagram of the steering system 160,acceleration system 162, and deceleration system 164 and identifiesexample relationships between the user input devices which a driver usesto control the vehicle in the manual (or semiautonomous) driving modes,computing devices 110 which generates control commands to control thevehicle in the autonomous driving modes, and the actuators which sendinstructions to the hardware that control the orientation and speed ofthe vehicle. In this regard, each actuator may include one or morecomputing devices having one or more processors and memory which may beconfigured the same or similarly to computing devices 110, processors120, and memory 130.

For instance, a steering input 210 (e.g. steering wheel or other device)of the vehicle can be used by the driver to cause the steering actuator220 of the steering system 160 to control the orientation of the wheelsusing the orientation control hardware 230 which may include thevehicle's axles and other hardware that can change the orientation ofthe vehicle's wheels. For example, as shown in FIG. 2A, steering inputsto the steering input 210 are sent to the steering actuator 220 whichconverts those inputs into corresponding steering control signals whichcan be acted upon by the orientation control hardware 230. Dependingupon the configuration of the vehicle, drive-by-wire or a mechanicalconnection, these steering inputs may be converted to electronic signalsbefore being received by the steering actuator or may be receivedphysically by a hardware connection to the steering actuator. Similarly,as shown in FIG. 2B, the computing devices 110 may send commands to thesteering actuator 220 to cause the steering actuator 220 to sendcorresponding steering control signals to the orientation controlhardware 230 to control the orientation of the wheels. For example,using the curvature of the trajectory, one or more derivatives severalderivatives of curvature), as well as a model of the vehicle and thevehicle's underlying suspension kinematics, the corresponding tire anglemay be determined. In addition, a closed loop control may be used tomodifies the commanded tire angle in order to ensure that the vehiclefollows the trajectory, for example in order to adjust the tire angle tomeet the trajectory using real-time feedback about the current tireangle.

The brake pedal 212 can be used by the driver to cause the brakingactuator 222 of the deceleration system 162 to control the position ofthe brakes 232. For example, as shown in FIG. 2A, inputs to the brakepedal 212 are sent to the braking actuator 222 which converts thoseinputs into braking control commands which can be acted upon by thebrakes 232. Depending upon the configuration of the vehicle,drive-by-wire or a mechanical connection, these braking inputs may beconverted to electronic signals before being received by the brakingactuator or may be received physically by a hardware connection to thebraking actuator. Similarly, as shown in FIG. 2B, the computing devices110 may send commands to the braking actuator 222 to cause the brakingactuator to send corresponding braking control commands to control theposition of the brakes.

The accelerator pedal 214 can be used by the driver to cause theacceleration actuator 224 of the acceleration system 164 to control theamount of fuel or energy sent by a fuel or power control system 234 tothe engine or motor which in turn, controls the speed of rotation of thevehicle's wheels. The power control system may thus control the amountof fuel (e.g. gasoline, diesel, etc.) or power (from one or morebatteries) to the engine or motor of the power system 174. For example,as shown in FIG. 2A, inputs to the accelerator pedal 214 are sent to theacceleration actuator 224 which converts those inputs into accelerationcontrol commands which can be acted upon by the power control system234. Similarly, as shown in FIG. 2B, the computing devices 110 may sendacceleration commands to the accelerator pedal 214 to cause theacceleration actuator to send acceleration control signals to the fuelor power control system 234 of the power system 174 in order to controlthe amount of fuel or energy sent to the engine or motor.

The memory 130 of computing device 110 and/or the memory of theactuators or one or more other computing devices may store configurationinstructions to allow the vehicle 100 to operate in different modesincluding a first driving mode which is a manual driving mode as well asone or more autonomous driving modes. In the manual driving mode, adriver is able to control the deceleration, acceleration, and steeringof a vehicle at the user inputs, such as the steering input 210, thebrake pedal 212, and the accelerator pedal 214. In addition, vehicle 100is configured via the configuration instructions such that commands fromthe computing devices 110 to control the actuators of the decelerationsystem 162, acceleration system 164, and steering system 160 are givenno priority. In other words, in the manual driving mode, commands fromthe computing devices 110 are invalid or ignored by the steeringactuator 220, braking actuator 222, and acceleration actuator 224. Inthis way, the driver is guaranteed that the autonomous driving controlsystem will not interfere with operation of vehicle 100.

In a second driving mode, or a first autonomous driving mode, thecomputing devices 110 may expect that a driver is presently in vehicle100 and capable of controlling the vehicle in the manual driving mode.In other words, the computing devices 110 are configured via theconfiguration instructions to readily allow transitions from the seconddriving mode to the first driving mode or rather, from first autonomousdriving mode to the manual driving mode. Vehicle 100 is also configuredsuch that commands originating from the user inputs, such as thesteering input 210, the brake pedal 212, and the accelerator pedal 214are given priority over commands from the computing devices 110. In thisregard, the driver is able to readily take control by using any of thesteering input 210, the brake pedal 212, and the accelerator pedal 214of vehicle 100. At the same time, the driver is guaranteed by both thecomputing devices 110 and the steering, braking and accelerationactuators that driver inputs will be prioritized over those of thecomputing devices 110.

The first autonomous driving mode may also have a plurality of differentsub-modes or configurations which allows for different levels ofautonomy in different environments. For instance, the first autonomousdriving mode may have a first configuration that allows for afully-autonomous driving mode in specific areas of a pre-mappedenvironment, but semi-autonomous driving modes (e.g. where a drivercontrols speed and/or steering) everywhere else. A second configurationmay allow a driver to adjust to increase the sensitivity of vehicle 100to transitions to manual driving mode, for instance, where a driverprefers to more easily change vehicle 100 from the first autonomousdriving mode to a semi-autonomous or the manual driving mode.

The first autonomous driving mode may also include a third configurationwith additional modifications to allow for safe testing of vehicle 100when a test driver is present. In order to have a redundant and morereliable means of guaranteeing test driver takeover ability, thetransition between the first driverless mode and manual driving mode maybe implemented in two different places: the computing devices 110 and ateach actuator. The actuator software may be considered well vetted andfixed due to extensive testing and may not change very often. However,the software of the computing devices 110 may be changed and testedregularly. Because the actuators may transition to the manual drivingmode independently of the computing devices 110, commands from thecomputing devices 110 which are improper (i.e. those which continue eventhough there is a transition to the manual driving mode) are invalid andignored. This transition may occur, for example, by having a driver (ortest driver) take control of one or more of steering, braking, oracceleration. This allows for the safe and effective testing of new orupdated software at the computing devices 110.

In a third driving mode, or a second autonomous driving mode, thecomputing devices 110 may expect that a driver is not presently invehicle 100 and capable of controlling vehicle 100 in the manual drivingmode. In this configuration, both the actuators and computing devices110 are configured via the configuration instruction to limit the impactof human inputs and transitions to the first driving more or the manualdriving mode in order to guarantee the safety of passengers and vehicle100. In other words, the first autonomous driving mode may be “easier”to enter than the second autonomous driving mode in order to limit useof the second driving mode to situations in which there is no drivercapable of controlling vehicle 100 present.

As with the first autonomous driving mode, the second autonomous drivingmode may include a plurality of different sub-modes or configurations.As an example, a first configuration may be a fully autonomous“driverless transportation service” mode which can be used to allowvehicle 100 to provide transportation services to passengers or users ofthe transportation service. This configuration may prevent vehicle 100from starting a trip if the vehicle does not meet certain conditions,such as if the vehicle is dirty, a door is open, passengers are notsitting in seats and/or do not have seat belt bucked, the vehicle isoverloaded (there is too much weight in the vehicle's seats and/or cargocompartments), etc. This configuration may also utilize a partition toprevent passengers from reaching manual controls (steering wheel, brakepedal, acceleration pedal, etc.).

This first configuration may also allow vehicle 100 to acceptinstruction from a dispatching server such as the server computingdevices 410. For instance, when in the first configuration of the secondautonomous driving mode, vehicles may be dispatched and/or staged by theserver computing devices 410 to locations where a vehicle can safelywait to be assigned a trip. This may include sending a vehicle to aspecific location, for instance, waiting at a specific shaded area neara mall, or sending a vehicle to a specific area, for instance, aspecific square mile or more or less to drive around and wait for anassignment. Similarly, vehicles may be limited to trips in certain areasas discussed above using, for instance, the second configuration of thesecond driving mode or by sending vehicle 100 to that area and usinggeo-fencing to limit movements of the vehicle to within certain areas.This may allow the dispatching servers to confirm that vehicles are sentonly where needed, and thereby allow more efficient staging and use of afleet of vehicles.

A second configuration may be similar to the first configuration, butwith some limitations determined based on the current status of vehicle100. For instance, vehicle 100 may be prevented from entering specificregions, such as school zones, highways, etc., based on the vehicle'scomputing device's current software version, state of the vehicle'ssensors (whether all are operating within normal parameters and/orwhether the sensors were calibrated within some predetermined number ofmiles or period of time, such as 100 miles or more or less or 24 hours),etc. In this regard, if vehicle 100's sensors have not been calibratedat a depot within the last 100 miles or last 24 hours, the vehicle maynot be able to drive on highways or in school zones. For instance, ifcertain sensors, such as radar or cameras, are not recently calibrated,the vehicle may need to avoid unprotected left turns or certainintersections having traffic lights at certain relative positions.

The second autonomous driving mode may also include a thirdconfiguration for testing vehicle 100. In this example, the computingdevices may control vehicle 100 according to the configurationinstructions as if the vehicle were operating in the firstconfiguration. However, a test driver, rather than taking control ofsteering, acceleration, or deceleration, may use an “emergency stopping”button to immediately stop vehicle 100 in the event of a problem. Inthis regard, vehicle 100 may apply all braking power availableimmediately to stop the vehicle as quickly as possible. Generally,because such immediate stopping is not appropriate for when vehicle 100is providing transportation services, the emergency stopping button maynot be available (i.e. may be removable) when operating in the firstconfiguration. In such cases, vehicle 100 may be stopped by a passengerusing a pull over request via the passenger's client computing device ora pull over button of the vehicle.

Example Methods

In addition to the operations described above and illustrated in thefigures, various operations will now be described. It should beunderstood that the following operations do not have to be performed inthe precise order described below. Rather, various steps can be handledin a different order or simultaneously, and steps may also be added oromitted.

As noted above, the vehicle 100 may be configured to allow differentsystems to implement thermal derating depending on whether the vehicleis operating in a manual driving mode, such as the first driving mode,or in an autonomous driving mode, such as the second or third drivingmode. For instance, the steering system may control its own thermalderating when the vehicle is operating in the manual mode, and theautonomous driving control system may implement the thermal deratingwhen operating in the autonomous driving modes.

FIG. 6 provides an example flow diagram 600 for operating a vehiclehaving a manual driving mode and an autonomous driving mode. The diagrammay represent steps taken by various features of the vehicle, such asone or more processors of the steering system and/or the one or moreprocessors 120 of the one or more computing devices 110, or anothercomputing device of the vehicle, etc. For instance, at block 610, thevehicle is controlled by one or more processors of an autonomous drivingcontrol system in the autonomous driving mode by generating controlcommands and sending the control commands to the steering system. Forinstance, returning to FIG. 2B, when the vehicle is operating in anautonomous driving mode, the planning system 168 may generatetrajectories based on information from the positioning system 170,perception system 172, and other systems of the vehicle. The computingdevices 110 may use these trajectories to generate control commands, forinstance steering commands, which are sent to the steering actuator 220of the steering system 160.

Returning to FIG. 6, at block 620, a steering system having one or moreprocessors is used to control the orientation of the one or more wheelsbased on control commands. As depicted in FIG. 2B, the steering actuator220 may use the control commands or steering commands to generate andsend corresponding steering control signals to the orientation controlhardware 230. In response, the orientation control hardware 230 maycontrol the orientation of the wheels in accordance with the trajectory.

Returning to FIG. 6, at block 630, first temperature information for thesteering system is used by the one or more processors of the steeringsystem to thermally derate the steering system when the vehicle isoperating in the manual drive mode. For instance, when the vehicle isbeing operated in the manual driving mode or any autonomous drivingmode, the steering system may generate temperature informationidentifying a measured or estimated temperature of the steering systemor one or more specific components of the steering system. In thisregard, the steering system may include one or more temperature sensorssuch as thermistors, thermometers, etc. or other devices for measuringdifferent parameters in order to measure temperature. These temperaturesensors may be located at any number of critical temperature areas forthe steering system such as the motor phase control power stages (whichmay include metal-oxide-semiconductor field-effect transistor orMOSFETs), voltage regulators, power inverters, printed circuit board(PCB), An application-specific integrated circuits (ASICS),microcontrollers, motor stator and rotor windings, cable harness,connectors, etc. Typically the most critical temperature area for thesteering system is the motor phase control power stages, as they may becarrying the highest electrical current, and are usually the hottest andmost critical components in the steering system.

The steering system and/or the autonomous driving control system may usefeedback from these temperatures sensors or other sources to determinetemperature information for the steering system. For example, one ormore processors of the steering system 160 or the computing devices 110or another computing device of the vehicle can determine, for instanceby modeling or estimating, the temperature of the steering system viathe feedback or by using other measured parameters such as electricalcurrent.

For instance, when the vehicle is operating in the manual driving mode,the steering system may compare the temperature information to one ormore thresholds. When the measured or estimated temperature of one ormore components of the steering system meets or is greater than one ormore maximum thresholds, the steering system may automatically limit theamount of torque applied in order to reduce the likelihood of furtherincreasing the temperature of the components and causing long-termdamage to the hardware. For instance, the steering system may reduce themaximum amount of torque available to control the orientation of the oneor more wheels when the vehicle is operating in a manual drive mode. Inthis regard, the steering system may automatically limit the amount oftorque that can be applied to the wheels to below a predeterminedamount. As one example, the steering system may automatically limit theamount of torque generated by the motor. This limit may increase as thespeed of the vehicle increases such that zero torque is allowed at zeromph and increases as the speed increases. In this regard, as thetemperature of the steering system or one or more specific components ofthe steering system increases, the limits may be decreased therebyattempting to reduce the thermal load on the steering system.

Returning to FIG. 6, at block 640, second temperature information forthe steering system is used by the one or more processors of theautonomous driving control system to thermally derate the steeringsystem when the vehicle is operating in the autonomous driving mode.When the vehicle is operating in an autonomous driving mode, theautonomous driving control system may also determine when to implementthe derating. Like the steering system, the autonomous driving controlsystem may also receive and/or determine the temperature information andcompare this information to the one or more maximum temperaturethresholds. Based on whether any of these maximum temperature thresholdsare met, the autonomous driving control system may limit the steeringangle and/or torque at the wheels or by reducing a maximum torqueavailable to control the orientation of the one or more wheels, andthereby automatically attempting to reduce the temperature of thesteering system or one or more specific components of the steeringsystem the steering system. As an example, this thermal derating by theautonomous driving control system may be implemented at the planningsystem 168 as constraints on steering angle and/or torque at the wheels.In this regard, the planning system 168 may attempt to generatetrajectories that control the vehicle within the aforementionedconstraints on steering angle and/or torque.

Because the thermal derating is implemented at the autonomous drivingcontrol system when the vehicle is operating in an autonomous drivingmode, in the event of a safety critical situation, the planning system168 may be able to ignore these constraints when generatingtrajectories. Safety critical situations may include situations whichwould otherwise result in the vehicle colliding with another object orwould prevent the vehicle from pulling over in an emergency such as whenthe autonomous driving control system has experienced an error, forinstance, an error in any of the systems of the autonomous drivingcontrol system such as the perception system perceiving an object “toolate” such that the vehicle has to swerve around the object or betterperformance in the steering system is required in order to control thevehicle to avoid a collision, etc. For instance, such constraints may beadjusted downwards or otherwise ignored when the planning system 168 isunable to solve for a trajectory that avoids a collision with an object.In this regard, a steering maneuver to avoid an object, which may nothave been possible if the steering system were implementing the thermalderating, may still be possible. The autonomous driving control systemmay then simply continue to send steering commands to the steeringsystem. Thus, whether or not there is derating may be controlledentirely at the autonomous driving control system when operating thevehicle in an autonomous driving mode.

The autonomous driving control system may control the thermal deratingin this way in any of the aforementioned autonomous driving modes, orrather whether or not there is a human driver available and thus in bothautonomous driving modes which require a human driver as well as thosethat do not require a human driver. For instance, in response tosteering command or other control signal from the autonomous drivingcontrol system, the steering system may be configured to automaticallyignore or simply stop generating the temperature information, ignore anyflags generated by comparing the measured or estimated temperature toone or more temperature thresholds), and/or only follow commandsreceived from the autonomous driving control system and ignore anytemperature information or thermal derating signals generated by thesteering system itself.

In order to better enable the aforementioned configuration of thevehicle where the steering system controls the thermal derating when thevehicle is in the manual driving mode and the autonomous driving controlsystem controls the thermal derating when the vehicle is in anautonomous driving mode, control commands coming from the steering input210 may be differentiated or distinguished from control commands comingfrom the autonomous driving control system. To facilitate this, thesignals themselves may include different content or characteristics,such as a flag or field that identifies the control signal as comingfrom the steering input 210 (manual driving mode) or the computingdevices 110 (autonomous driving modes).

Alternatively, rather than different types of signals, the steeringsystem may have different interfaces for control commands which comefrom different sources (e.g. one for the manual mode and another for anyautonomous driving modes). For instance, in a manual driving mode, the“interface” could simply be torque which is applied by the driver to thehandwheel being transferred mechanically via the steering column to thesteering rack. For a drive-by-wire system, a control module in thesteering column may convert the driver input into electrical signals,either hardwired to the steering rack or transmitted via a communicationbus. For the autonomous control driving system, the interfaces could behardwired (ex. analog, digital, pulse width modulation, etc.) or theinterfaces could involve signals transmitted via one or morecommunication buses. In certain situations, to maintain safety, thesteering system may cause the vehicle to operate only in the manualdriving mode. For example, if the derating will allow only 50% or moreor less of the possible torque generated by the motor, the steeringsystem may send a signal to the autonomous driving control system and/orthe actuators to cause the vehicle to switch from the autonomous to amanual driving mode when the vehicle is operating in an autonomousdriving mode that requires a human driver. In this regard, theautonomous driving control system may stop sending steering,deceleration, and/or acceleration commands to the steering actuator 220,braking actuator 222, and/or acceleration actuator 224. In addition oralternatively, the steering actuator 220, braking actuator 222, andacceleration actuator 224 may ignore commands from the computing devices110 and only respond to inputs from the steering input 210, brake pedal212, and/or accelerator pedal 214. Of course, when the vehicle isoperating a vehicle in an autonomous driving mode which does not requirea human driver, such a process may be inappropriate.

As noted above, the thermal derating may protect components fromunnecessary long-term damage to the hardware. The thermal derating maybe especially important at lower speeds or when the vehicle is at rest,so that frequent and/or small changes in commanded tire position do notincrease the heat of the steering system or unnecessarily cause wear tothe front tires. As an example, moving a wheel (or a tire) against acurb when the vehicle is not otherwise moving can create significantfriction and heat. In this regard, the autonomous driving control systemmay be permitted to still implement the thermal derating when thevehicle is moving at or below certain predetermined threshold speeds,such as 10 kilometers per hour or more or less. At lower speeds, this isa greater ability to build heat at the components of the steering systemfaster. As such, even when the planning system 168 “ignores” constraintsrelated to thermal derating, the autonomous vehicle control system maystill implement thermal derating when sending signals to the steeringsystem.

The features described herein may provide for a useful and practicalapproach to addressing thermal derating for autonomous vehicles in a waywhich may improve overall safety of these vehicles. By moving thethermal derating functionality of the steering system into theautonomous driving control system when in an autonomous driving mode,this enables the vehicle to respond to safety critical situationsregardless of whether the steering system would otherwise have beenderating itself.

Unless otherwise stated, the foregoing alternative examples are notmutually exclusive, but may be implemented in various combinations toachieve unique advantages. As these and other variations andcombinations of the features discussed above can be utilized withoutdeparting from the subject matter defined by the claims, the foregoingdescription of the embodiments should be taken by way of illustrationrather than by way of limitation of the subject matter defined by theclaims. In addition, the provision of the examples described herein, aswell as clauses phrased as “such as,” “including” and the like, shouldnot be interpreted as limiting the subject matter of the claims to thespecific examples; rather, the examples are intended to illustrate onlyone of many possible embodiments. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

1. A vehicle comprising: a steering system having one or more processorsconfigured to control the orientation of one or more wheels of thevehicle based on control commands; and an autonomous driving controlsystem having one or processors configured to: control the vehicle in anautonomous driving mode by generating the control commands, and send thecontrol commands to the steering system, and wherein the one or moreprocessors of the steering system are further configured to thermallyderate the steering system based on first temperature information forthe steering system when the vehicle is operating in a manual drivemode, and the one or more processors of the autonomous driving controlsystem are further configured to thermally derate the steering systembased on second temperature information for the steering system when thevehicle is operating in the autonomous driving mode.
 2. The vehicle ofclaim 1, wherein the one or more processors of the autonomous drivingcontrol system are further configured to, when operating in theautonomous driving mode, limit thermal derating in order to enable atype of maneuver that the vehicle needs to perform to avoid an object.3. The vehicle of claim 2, wherein the type of maneuver includes asteering maneuver to avoid an object.
 4. The vehicle of claim 2, whereinthe type of maneuver includes pulling the vehicle over in response to afault with the autonomous driving control system.
 5. The vehicle ofclaim 1, wherein the one or more processors of the autonomous drivingcontrol system are further configured to, when the vehicle is operatingin the autonomous driving mode, limit thermal derating when the vehicleis traveling at speed greater than a predetermined threshold speed. 6.The vehicle of claim 1, wherein when the vehicle is operating in theautonomous driving mode, the one or more processors of the steeringsystem are further configured to ignore temperature informationgenerated by the steering system.
 7. The vehicle of claim 1, whereinwhen the vehicle is operating in the autonomous driving mode, the one ormore processors of the steering system are further configured to ignoreany thermal derating signals generated at the steering system.
 8. Thevehicle of claim 1, wherein the one or more processors of the steeringsystem are further configured to distinguish between the controlcommands and signals generated by manual operation of a steering inputof the vehicle.
 9. The vehicle of claim 1, wherein the one or moreprocessors of the steering system are further configured to distinguishbetween the control commands and signals generated by manual operationof a steering input of the vehicle based on content of the controlcommands and the signals.
 10. The vehicle of claim 1, wherein the one ormore processors of the steering system are further configured todistinguish between the control commands and signals generated by manualoperation of a steering input of the vehicle using different interfacesfor receiving the control commands and the signals.
 11. The vehicle ofclaim 1, wherein the one or more processors of the steering system arefurther configured to cause the vehicle to switch from the autonomousdriving mode to the manual driving mode when thermal derating reducesavailable torque at the one or more wheels below a predetermined amount.12. A method of operating a vehicle having a manual driving mode and anautonomous driving mode, the method comprising: controlling, by one ormore processors of an autonomous driving control system, the vehicle inthe autonomous driving mode by generating control commands and sendingthe control commands to a steering system having one or more processors;using the steering system to control the orientation of the one or morewheels based on control commands; using, by the one or more processorsof the steering system, first temperature information for the steeringsystem to thermally derate the steering system when the vehicle isoperating in the manual drive mode; and using, by the one or moreprocessors of the autonomous driving control system, second temperatureinformation for the steering system to thermally derate the steeringsystem when the vehicle is operating in the autonomous driving mode. 13.The method of claim 12, further comprising, when the vehicle isoperating the autonomous mode, overriding any thermal derating in orderto enable a type of maneuver that the vehicle needs to perform to avoidan object.
 14. The method of claim 13, wherein the type of maneuverincludes a steering maneuver to avoid an object.
 15. The method of claim13, wherein the type of maneuver includes pulling the vehicle over inresponse to a fault with the autonomous driving control system.
 16. Themethod of claim 12, further comprising, when the vehicle is operating inthe autonomous driving mode, overriding any thermal derating when thevehicle is traveling at speed greater than a predetermined thresholdspeed.
 17. The method of claim 12, further comprising, when the vehicleis operating in the autonomous driving mode, ignoring, by the one ormore processors of the steering system, temperature informationgenerated by the steering system.
 18. The method of claim 12, furthercomprising, when the vehicle is operating in the autonomous drivingmode, ignoring, by the one or more processors of the steering system,any thermal derating signals generated at the steering system.
 19. Themethod of claim 12, further comprising, causing, by the one or moreprocessors of the steering system, the vehicle to switch from theautonomous driving mode to the manual driving mode when thermal deratingreduces available torque at the one or more wheels below a predeterminedamount.